Semiconductor devices have long been under continual development. Some of these development efforts have been largely geared towards seeking to improve the communications between these semiconductor devices. There is typically a large degree of undesirable coupling of signals between pads, traces, and devices within composite metal oxide semiconductor (CMOS) devices. The operating voltage levels of many CMOS devices involves employing a 0-3.3 Volt (V) swing; a 0-3.3 V level signal is employed to couple information from one device to another within many prior art CMOS device systems. This level of voltage may cause a high degree of interference for many of the neighboring high performance devices. This noise, undesirably coupled from the use of these relatively high CMOS voltage levels, will appear in the form of distortion, increased noise, and create data dependent errors within the system. This generates an undesirable feedback path within the system that will corrupt much data.
Particularly within high performance devices, this undesirable coupling of noise will induce significant deleterious effects within the overall system. These deleterious effects may surface in the form of distortion, increased noise, reduced data throughput, data errors, and other degradation in performance. One categorization of high performance devices would include those devices that operate having a signal to noise ratio (SNR)>90 dB and a total harmonic distortion (THD)>90 dB.
As an illustrative example within such a high performance device receive (RX) front-end, the analog to digital converter (ADC) output is usually observed to check on the performance of the system. If this output is sent off chip using standard digital composite CMOS output pads, then these pads become a strong source of signal-dependant substrate noise. Given the high gain through the RX signal path, a very small signal amount of coupling back into the signal inputs or the reference input of the ADC will undesirably create significant distortion in the final ADC output. The MSB (most significant bit) of the ADC output (in 2's complement form) represents the sign of the input data and has significant signal content. The bits after the MSB start to have less signal dependence progressing from the MSB to the LSB (least significant bit). These other bits hence can be considered more as sources of noise.
Further limitations and disadvantages of conventional and traditional systems will become apparent through comparison of such systems with the invention as set forth in the remainder of the present application with reference to the drawings.